The goal of this project is to examine reasons for the 3-fold survival difference observed between African-American and Caucasian women age 20-54 in Atlanta newly diagnosed with invasive breast cancer. The study focuses on three issues: 1. the extent of racial differences in the aggressiveness of breast cancers and the contribution of method of detection to racial differences in tumor aggressiveness, 2. the effects of adolescent exposure to several hormone-related breast cancer risk factors and of the method of breast cancer detection on tumor aggressiveness and on racial differences in tumor aggressiveness, and 3. the contribution of tumor aggressiveness to poorer survival among black women. This project builds on information already collected on 841 women with invasive breast cancer (246 African-American, 595 Caucasian) and 914 controls (251 African-American and 633 Caucasian) who were interviewed as part of an N.C.I. - initiated population-based, case-control study of breast cancer etiology in young women (N01-CP-95642-32). All women newly diagnosed with invasive breast cancer in Fulton, DeKalb and Cobb Counties in Georgia during 5/1/90 - 12/31/92 were rapidly identified and 87% of African-American women with breast cancer and 90 percent of Caucasian women with breast cancer were interviewed. A sample of controls was selected from the same counties during the same time period and 83 percent were interviewed. This patient cohort will be followed for recurrence and mortality through April 2000. Patient interview information is already available on screening history, method of cancer detection and on the primary risk factors of interest: early menarche and adolescent exposure to oral contraceptive use, spontaneous and induced abortion, childbirth, and obesity. A detailed pathologic review will be conducted and two markers of cell proliferation will be measured in formalin-fixed, paraffin embedded tissues: S-phase fraction determined by flow cytometry and Ki-67 by immunocytochemical staining. Four other well characterized markers of tumor aggressiveness are a focus of this analysis: aneuploidy (DNA content measured by flow cytometry), expression of c-erbB-2 and p53 gene products (detected by immunocytochemistry), and vascular response (determined by image quantification of vascular density). The study includes information on a variety of additional characteristics which affect risk and/or survival.